It is known to prepare ketoximosilanes by reacting alkyltrichlorosilanes with ketoximes; see, for example, German Auslegeschrift 1 301 140, published European Application 0 082 324, Soviet Patent No. 435 243 and Soviet Patent No. 724 514. The performance of these processes always involves the risk that the ketoxime and ketoximosilane come in contact with inorganic substances of a strong acid nature. The resulting intermediate hydrogen chloride then forms the hydrochloride of the ketoxime. For example, methylethylketoxime boils under normal pressure at 152.degree. C. without decomposing, whereas the hydrochloride thereof vigorously decomposes at 50.degree. to 70.degree. C. Such decompositions, moreover, can be triggered by catalytic amounts of FeCl.sub.3, for example. Under such conditions, ketoximosilanes also tend to undergo explosive decompositions. L. J. Tyler reports on two violent explosions of this type in Chemical Engineering News, 52 (1974), No. 35, 3.
It is also known to prepare ketoximosilanes by reacting organochlorosilanes with ketoximes in the presence of suitable acid acceptors and solvents; see, for example, U.S. Pat. No. 3,962,160, U.S. Pat. No. 3,441,583, U.S. Pat. No. 3,341,486, U.S. Pat. No. 3,817,909, German Auslegeschrift No. 1 301 140, German Auslegeschrift No. 1 120 640, German Auslegeschrift No. 1255 924, French Patent No. 1,118,495, European Patent No. 0 036 262, published European Application No. 0 293 306, and W. Noll, Chemie und Technologie der Silikone, page 342, published by Verlag Chemie, Weinheim 1968).
In these known processes, solid ammonium salts such as ammonium chloride or amine hydrochlorides are obtained as byproducts, depending upon the type of acid acceptor which is used. They precipitate in very finely dispersed form and are therefore relatively difficult to filter or wash out. In these processes, too, there is the danger of the above described explosion-like decompositions, for instance, due to formation of so called "acid nests" or even minor metering errors.
The filtrate obtained by filtering the products formed in the above mentioned processes contains the desired oximosilane, which frequently remains in the sump as a colored substance containing ammonium chloride after the solvent is distilled off. A subsequent distillation of the particular ketoximosilane must take place in a vacuum. This operational step involves a great amount of labor and cost, and is not entirely safe because it approaches the thermal stability of the ketoximosilanes.